Wireless mems left atrial pressure sensor

ABSTRACT

Systems for monitoring left atrial pressure using implantable cardiac monitoring devices and, more specifically, to a left atrial pressure sensor implanted through a septal wall are presented herein.

FIELD OF THE INVENTION

Aspects of the present disclosure relate to systems and methods relatedto implantable cardiac monitoring devices and, more specifically, to aleft atrial pressure sensor implanted through a septal wall.

BACKGROUND OF THE INVENTION

Monitoring the left atrial pressure (LAP) of heart failure patients isan effective method of assessing and managing a patient's heart failureprogression. Timely interventions including medication taken asimmediately as possible after an increase in LAP would more effectivelytreat a patient and reduce unnecessary hospitalization. To date, devicesand approaches to monitor surrogates of LAP have encountered significanttechnical challenges.

Hemodynamic monitoring systems using other measurements as a surrogatefor direct measurement of LAP have been tested in clinical trials withmixed results. Lead-based pressure sensors situated in the rightventricle outflow tract (RVOT) were relatively ineffective in managingheart failure and were additionally vulnerable to lead-relatedreliability issues. Wireless MEMS pressure sensors situated in thepulmonary artery are ill-suited for at least a subpopulation of patientspresenting with heart failure. For example, the assessment of LAP usingsurrogate measurements within the pulmonary artery may not be suitablefor patients suffering from pulmonary hypertension or other pulmonaryconditions.

A silicone lead-based LAP sensor has been shown to be relativelyeffective at managing heart failure in initial feasibility studies.However, silicone-based leads used in other medical devices haveexhibited a vulnerability to reliability-related performancedegradation. In addition, obtaining LAP measurements using the siliconelead-based LAP sensor may present several challenges that may beexacerbated by the routing of the leads necessary for the operation ofthe pressure sensor. In particular, access to the left atrium of theheart must be provided in a safe manner and the pressure sensors need tobe implanted in a manner that ensures accurate pressure measurements andthat minimizes the risk of device-related complications such as thrombusformation.

A need exists for improved devices and techniques for measuring LAPsafely and accurately. In addition, a need exists for improved devicesand techniques for measuring LAP that reduce the need for invasiveprocedures to operate and maintain the LAP measurement device, and thatreduce the need for intrusive associated elements such as device leadsto power the device and/or to transmit a signal encoding the measuredLAP. Such a device would facilitate the safe and accurate monitoring ofLAP, thereby enhancing the timeliness and quality of the treatment ofheart failure in variety of patient populations.

BRIEF SUMMARY OF THE INVENTION

This disclosure presents a novel concept of the wireless MEMS LAP sensorand tools used to safely place the wireless MEMS sensor in the leftatrium. A wireless LAP sensor would eliminate negative perceptionsassociated with silicone bodied leads and device-pocket infections andwould provide clinicians hemodynamic data that is considered to be thegold standard for heart-failure management.

Disclosed herein is a wireless and leadless left atrial pressuremeasurement device configured for delivery through a thickness of anatrial septum via a minimally invasive delivery tool. In a firstembodiment, the device includes a wireless pressure sensor, a firstanchoring element, and a second anchoring element. The wireless pressuresensor includes a proximal portion, a distal portion opposite theproximal portion, and a housing containing a hermetically sealed cavitycontaining a sensor circuit. The first anchoring element includes afirst distal end and a first free proximal end generally opposite thefirst distal end. The first distal end is operably coupled to thewireless pressure sensor. The first anchoring element extends proximallyaway from the proximal portion. The second anchoring element includes asecond distal end and a second free proximal end generally opposite thesecond distal end. The second distal end is operably coupled to thewireless pressure sensor. The second anchoring element extendsproximally away from the proximal portion. When the first and secondanchoring elements are free to assume a biased state, the first freeproximal end and second free proximal end extend in generally oppositedirections and the first anchoring element projects generally distally.

In one version of the first embodiment, the first anchoring element isconfigured such that, when the device is being delivered via thedelivery tool, the first anchoring element is deflected away from thebiased state via the delivery tool such that the first and second freeproximal ends are in close proximity to each other and projectinggenerally proximally away from the proximal portion. In one version ofthe first embodiment, in the biased state, the first free proximal endis in close proximity to the distal region as compared to the secondfree proximal end. In one version of the first embodiment, in the biasedstate, the first anchoring element extends along a longitudinal side ofthe wireless pressure sensor offset from the longitudinal side. In oneversion of the first embodiment, in the biased state, the firstanchoring element extends along a longitudinal side of the wirelesspressure sensor offset from the longitudinal side. In one version of thefirst embodiment, in the biased state, the first anchoring element andthe wireless pressure sensor combine to form a clamping arrangement.

In one version of the first embodiment, the clamping arrangementcomprises a distance between the first anchoring element and thewireless pressure sensor that is slightly less than the thickness of theatrial septum. In one version of the first embodiment, the devicefurther includes a silicone disc seal immediately adjacent the proximalportion and through which at least one of the first or second anchoringelement extends.

In one version of the first embodiment, the device further includes afeature extending from the proximal region and configured for engagementby a tether of the delivery tool. The feature includes a knob extendingfrom the proximal region. In one version of the first embodiment, thedevice further includes a feature including a knob, an extension plugand a lanyard. The lanyard is attached to the knob at one end and asecond end of the lanyard is attached to the proximal region.

In one version of the first embodiment, the first anchoring elementincludes a biocompatible resilient material. For example, thebiocompatible resilient material is selected from: platinum, NITINOL,silicone, polyurethane, plastic polyether block amide, high densitypolyethylene, silicone rubber, and any combination thereof. Theanchoring elements may be wire, flat sheets or a host of otherconfigurations.

In a second embodiment, the device includes a wireless pressure sensor,a first anchoring element, and a second anchoring element. The wirelesspressure sensor includes a proximal portion, a distal portion oppositethe proximal portion, and a housing containing a hermetically sealedcavity containing a sensor circuit. The first anchoring element issupported on the wireless pressure sensor between the proximal anddistal portions and includes first and second wings spaced apart fromeach other. When the first and second wings are in a biased state, thefirst and second wings extend radially outward from the wirelesspressure sensor. The second anchoring element is supported on thewireless pressure sensor between the proximal and distal portions andincludes third and fourth wings spaced apart from each other. When thethird and fourth wings are in a biased state, the third and fourth wingsextend radially outward from the wireless pressure sensor and the thirdand fourth wings face the first and second wings in an opposed, spacedapart fashion.

In one version of the second embodiment, the first and second anchoringelements are configured such that, when the device is being deliveredvia the delivery tool, the first, second, third and fourth wings aredeflected away from the biased state via the delivery tool such that thefirst and second wings project generally distally and the third andfourth wings project generally proximally. In one version of the firstembodiment, the first anchoring element and the second anchoring elementcombine to form a clamping arrangement. In one version of the firstembodiment, the clamping arrangement includes a distance between thefirst and second wings and the third and fourth wings that is slightlyless than the thickness of the atrial septum.

In one version of the second embodiment, the device further includes afeature on or near the proximal region and configured for engagement bya tether of the delivery tool.

In one version of the second embodiment, the first anchoring elementincludes a biocompatible resilient material. For example, thebiocompatible resilient material is selected from: platinum, NITINOL,silicone, polyurethane, plastic polyether block amide, high densitypolyethylene, silicone rubber, and any combination thereof.

Also disclosed herein is a wireless and leadless left atrial pressuresensor. In one embodiment, the sensor includes a housing, a flexiblediaphragm, a sensor, and a sensor circuit. The housing contains ahermetically sealed cavity. The sealed cavity opens at an openingdefined within a surface of the housing. The flexible diaphragm issealed over the opening to complete the hermetically sealed cavity. Thesensor circuit includes an induction coil, a fixed capacitor, and amoveable capacitor plate. The induction coil includes a first end and asecond end. The fixed capacitor plate is electrically connected to thefirst end of the induction coil. The moveable capacitor plate iselectrically connected to the second end of the induction coil andmechanically attached to the flexible diaphragm. The sensor circuit iscontained within the hermetically sealed cavity.

In one version of the embodiment, the fixed capacitor plate and themoveable capacitor plate form a variable capacitor. The capacitance ofthe variable capacitor varies as a function of a deflection of theflexible diaphragm in response to a left atrial pressure on thediaphragm. The induction coil and the variable capacitor form a resonantcircuit comprising a resonant frequency. The resonant frequency variesin response to a change in the left atrial pressure.

In one version of the embodiment, the left atrial pressure may beobtained using a data acquisition device including an external antennacoil. The external antenna coil magnetically couples with the inductioncoil of the sensor to transfer power to the sensor. The resonantfrequency of the sensor is determined by an analysis of a load impedanceof the sensor during the power transfer. The left atrial pressure isdetermined using a predetermined calibration of pressure as a functionof resonance frequency.

In one version of the embodiment, the housing is constructed from anon-conductive material selected from: fused silica, quartz, ceramic,and sapphire. The diaphragm is constructed from a non-conductivematerial selected from: fused silica, quartz, ceramic, and sapphire.

In one version of the embodiment, the diaphragm is constructed from aconductive material selected from: highly doped silicon and titanium.The diaphragm and the moveable capacitor plate are integrated into asingle structure and the diaphragm is electrically connected to thesecond end of the induction coil.

In one version of the embodiment, the diaphragm deflects to a maximumdeflection ranging from about 1 nanometer to about 100 micrometers. Inone version of the embodiment, the housing further comprises an externalshape selected from: a rectangular shape, a prismatic shape, and acylindrical shape.

Also disclosed herein is a method of implanting a wireless and leadlessleft atrial pressure measurement device into a left atrium of a patient.In a first embodiment, the method includes: obtaining the devicecomprising a sensor and at least one anchoring element, each anchoringelement comprising a free end and an attached end attached to thesensor; attaching the device to a catheter comprising a catheterproximal end, a catheter distal end, and a tether protruding from thecatheter distal end, wherein the tether is attached to each free end ofeach of the at least one anchoring elements; situating the device andthe catheter within a lumen of a sheath comprising a sheath proximal endand a sheath distal end, wherein: a) the sensor is situated nearest tothe sheath distal end; each of the at least one anchoring elements is ina folded configuration extending in a proximal direction within thelumen; and b) the tether extends from the free end of each of the atleast one anchoring elements in a proximal direction toward thecatheter; and advancing the catheter, sheath, and device through a holeformed in the atrial septum from the right atrium into the left atrium.

In one version of the first embodiment, the method further includesretracting the sheath to expose the sensor within the left atrium. Inone version of the first embodiment, the method further includesretracting the catheter, sheath and device together to situate thesensor against a left wall of the atrial septum in the left atrium. Inone version of the first embodiment, the method further includesretracting the sheath to expose the at least one anchoring elements,allowing the anchoring elements to elastically rebound from the foldedconfiguration to an anchoring configuration. In one version of the firstembodiment, the method further includes detaching the tether from eachfree end of the at least one anchoring elements, and retracting thecatheter and sheath from the patient. In one version of the firstembodiment, the method further includes compressing each of the at leastone anchoring elements from the anchoring configuration into the foldedconfiguration to fit the device into the sheath.

In a first embodiment, the method includes: obtaining the devicecomprising a sensor, at least one proximal anchoring element, and atleast one distal anchoring element, each anchoring element comprising afree end and an attached end attached to the sensor; attaching thedevice to a catheter comprising a catheter proximal end, a catheterdistal end, and a tether protruding from the catheter distal end,wherein the tether is attached to each free end of each of the at leastone proximal anchoring elements; situating the device and the catheterwithin a lumen of a sheath comprising a sheath proximal end and a sheathdistal end, wherein: a) each of the at least one distal anchoringelements is situated nearest to the sheath distal end in a first foldedconfiguration extending in a distal direction within the lumen; b) eachof the at least one proximal anchoring elements is situated in a secondfolded configuration extending in a proximal direction within the lumen;and c) the tether extending from the device in a proximal directiontoward the catheter; and advancing the catheter, sheath, and devicethrough a hole formed in the atrial septum from the right atrium intothe left atrium.

In one version of the second embodiment, the method further includesretracting the sheath to expose the one of more distal anchoring deviceswithin the left atrium and allowing the distal anchoring elements toelastically rebound from the first folded configuration to a firstanchoring configuration. In one version of the second embodiment, themethod further includes retracting the catheter, sheath and devicetogether to situate the one of more distal anchoring devices against aleft wall of the atrial septum in the left atrium. In one version of thesecond embodiment, the method further includes retracting the sheath toexpose the at least one proximal anchoring elements, allowing theanchoring elements to elastically rebound from the second foldedconfiguration to a second anchoring configuration. In one version of thesecond embodiment, the method further includes detaching the tether fromthe device and retracting the catheter and sheath from the patient. Inone version of the second embodiment, the method further includescompressing each of the at least one distal anchoring elements into thefirst folded configuration and each of the at least one proximalanchoring elements into the second folded configuration to fit thedevice into the sheath.

Also disclosed herein is a method of retrieving a wireless and leadlessleft atrial pressure measurement device from a left atrium of a patient,the method comprising: advancing a snare catheter situated within asheath into a right atrium of the patient; retracting the sheath toexpose a snare loop of the snare catheter; securing the snare looparound a knob or an extension plug projecting from the device; applyingtraction to the knob or the extension plug using the snare catheter towithdraw a sensor of the device from the atrial septum; applyingcountertraction using the sheath to deform each of at least oneanchoring elements of the device into a folded configuration and tosituate the device within the sheath; and retracting the snare catheter,sheath, and device from the patient.

While multiple embodiments are disclosed, still other embodiments of thepresent disclosure will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the disclosure. As will be realized, thedevices and methods disclosed herein are capable of modifications invarious aspects, all without departing from the spirit and scope of thepresent disclosure. Accordingly, the drawings and detailed descriptionare to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures illustrate various aspects of the technologydisclosed herein.

FIG. 1 is a cross-sectional view of a wireless LAP sensor devicesituated in a left atrium of a patient.

FIG. 2 is a side cross-sectional view of a wireless LAP sensor devicewith a pair of anchoring elements.

FIG. 3 is a cross-sectional view of a cylindrical wireless LAP sensordevice situated in a left atrium of a patient.

FIG. 4 is a cross-sectional view of a wireless LAP sensor devicesituated in a left atrium of a patient showing the anchoring forcesgenerated by the anchoring elements and sensor.

FIG. 5 is a side view of the wireless LAP sensor device illustrated inFIG. 2 showing anchoring elements in the form of wire frames. FIG. 5A isa cross-sectional view of an anchoring element of FIG. 5.

FIGS. 6A and 6B are a side view and a perspective view of a wireless LAPsensor device with anchoring elements in the form of thin sheets. FIG.6C is a linear profile of an anchoring element of FIGS. 6A and 6B.

FIG. 7A and FIG. 7B are a side view and a perspective view of a wirelessLAP sensor device with spoon-like anchoring elements. FIG. 7C is acurved profile of an anchoring element of FIGS. 7A and 7B.

FIG. 8 is a side view of a wireless LAP sensor device that includes asingle anchor element.

FIG. 9A is an end view and FIG. 9B is a side view of a wireless LAPsensor device that includes a “dual propeller” arrangement of sixanchoring elements.

FIG. 10 is a side view of a wireless LAP sensor device that includesfour anchoring elements situated against the left wall of the atrialseptum.

FIG. 11 is a side view of a wireless LAP sensor with the anchoringelements provided in the form of a wire frame.

FIG. 12 is a perspective view of a wireless LAP sensor device in which asilicone disc is attached near the base of the anchoring elements.

FIG. 13 is an exploded side view of the sensor with a portion of thehousing removed to view the sensor's interior.

FIG. 14 is an exploded diagram illustrating one technique for attachingthe flexible diaphragm to the housing.

FIG. 15 is an exploded diagram illustrating another technique forattaching the flexible diaphragm to the housing.

FIG. 16A is a cutaway side view and FIG. 16B is a cutaway top view of asensor illustrating the relationship of the various components of thesensor circuit.

FIG. 17 is a schematic diagram illustrating an idealized resonant sensorcircuit.

FIG. 18A is a perspective view and FIG. 18B is a side view of a sleevemounted on a proximal end of the sensor.

FIG. 19A is a perspective view and FIG. 19B is a side view of a sleevein another aspect that further includes an extension plug extendingalong the axis of symmetry of the anchoring elements to furtherfacilitate the snagging and/or retrieval of the sensor from the patient.

FIG. 20 is a flow chart illustrating a method of implanting a wirelessLAP sensor device in various aspects.

FIG. 21A is a side view of a catheter used to implant a wireless LAPsensor device. FIG. 21B is a side view of a dilator used to implant awireless LAP sensor device. FIG. 21C is a side view of a needle used toimplant a wireless LAP sensor device.

FIGS. 22A-D are side views of a wireless LAP sensor device and a sheathfor the delivery thereof, the device being illustrated at various stepsin the course of being implanted.

FIGS. 23A-G are various views of a wireless LAP sensor device and asheath for the delivery thereof, the device being illustrated at varioussteps in the course of being implanted.

FIG. 24 is a side view of a wireless LAP sensor device situated withinthe left atrium in which the device is anchored in place, but stillattached to the tethers.

Corresponding reference characters and labels indicate correspondingelements among the views of the drawings. The headings used in thefigures should not be interpreted to limit the scope of the claims.

DETAILED DESCRIPTION

Provided herein in various aspects of the disclosed technology arewireless left atrial pressure (LAP) sensor devices, methods ofdelivering the LAP sensor devices to situate and chronically anchor thedevice in the left atrium/atrial septum of a patient, and methods ofusing the device to monitor the left atrial pressure (LAP) of thepatient. In addition, a delivery/retrieval system for situating,chronically anchoring, and/or retrieving the wireless LAP sensor deviceis provided in various other aspects.

The wireless LAP sensor device includes a wireless LAP sensor attachedto at least one anchoring element. FIG. 1 is a cross-sectional view of awireless LAP sensor device 100 in one aspect. The wireless LAP sensordevice 100 includes a sensor 102 attached to at least one anchoringelement 104. At least a portion of the sensor 102 is situated within theleft atrium 106 of a patient. The at least one anchoring element 104 istypically situated against the right wall 110 of the atrial septum 108opposite to the sensor 102, as illustrated in FIG. 1. The at least oneanchoring element 104 may exert a modest anchoring force against theright wall 110 to securely attach the sensor 102 to the left wall 112 ofthe atrial septum 108 and to prevent dislodgement or embolization of thesensor 102. In another aspect (not shown), the wireless LAP sensordevice 100 may include at least one anchoring element 104 situatedagainst the left wall 112 as well as against the right wall 110 of theatrial septum 108 to provide a more robust anchoring of the sensor 102within the left atrium 106.

The sensor 102 incorporates circuitry (not shown) to implementcapacitive pressure sensing for monitoring LAP in a patient and tofurther implement inductive telemetry for remotely reading the measuredLAP using an external data acquisition device, which also functions as apower source for the sensor 102. The circuitry and mechanical elementsof the sensor 102 further incorporatemicromachined/microelectromechanical system (MEMS) elements designed toprovide sensitive measurements of pressure fluctuations within the leftatrium 106 housed within a relatively small implantable sensor 102.

The sensor 102 of the wireless LAP sensor device 100 may be situated andsecured within the left atrium 106 using a delivery/retrieval system(not shown) to perform modifications of proven surgical implantationtechniques. The sensor 102 and/or the at least one anchoring element 104may further include radioopaque coatings, radioopaque markings, and/orother landmarks visible using one or more medical imaging methods tofacilitate the visualization of the device 100 during implantation. Thesensor 102 and at least one anchoring element 104 may be furtherdesigned to be readily snagged, repositioned, and/or retrieved from theleft atrium/septum of the patient using the delivery/retrieval system toimplement additional modifications of proven surgical remediation and/orretrieval techniques.

Because inductive telemetry is used by the circuitry of the wireless LAPsensor device 100, electrical power is supplied to the sensor 102 viainductive power transfer by the external data acquisition device.Because this inductive power transfer obviates the need for aconventional power source such as a battery or other electrical powersource resident within the sensor 102 or electrically connected to thesensor 102 via electrical leads, the wireless LAP sensor device 100 mayremain fully operational over extended and chronic residence periodswithin the left atrium 102 of the patient. In addition, the circuitry ofthe wireless LAP sensor device 100 may be designed to be compatible withmore than one type of data acquisition device to enhance the operationalflexibility of the device 100.

Various aspects of the wireless LAP sensor device 100 including thesensor 102 and at least one anchoring element 104 are described infurther detail herein below. In addition, methods of implanting and orsituating the wireless LAP sensor device 100 into the left atrium 106 ofa patient, and methods of repositioning and/or retrieving the wirelessLAP sensor device 100 from the left atrium 106 of the patient using thedelivery/retrieval system are also described in further detail hereinbelow. Methods for monitoring LAP in a patient using the implantedwireless LAP sensor device 100 are also described in further detailherein below.

I. Wireless Left Atrial Pressure (LAP) Sensor Device

In various aspects, the wireless LAP sensor device 100 includes a sensor102 attached to at least one anchoring element 104. The sensor 102 issituated within the left atrium 106 of a patient, typically against theleft wall 112 of the atrial septum 108, as illustrated in FIG. 1. Thesensor 102 is secured in place by the anchoring elements 104, which maybe situated against the right wall 110 of the atrial septum 108, asillustrated in FIG. 1, and optionally against the left wall 112 of theatrial septum 108 in other aspects.

In one aspect, the sensor 102 situated in the left atrium 106 may bedesigned to have a relatively low profile against the left wall 112 ofthe atrial septum 108, as illustrated in FIG. 1. This low-profile sensordesign, including, but not limited to rectangular or prismatic shapes,may reduce the formation of blood clots within the left atrium 106 andmay enhance the build-up of a biological layer of endothelial cells(i.e., “the intima”) over the sensor 102 and the anchoring elements 104.As a result, the likelihood of blood clots forming and breaking loosemay be significantly reduced as compared to sensor designs that protruderelatively deeply into the left side of the heart. Blood clots breakingloose in the left side of the heart may travel to other areas of thebody such as the brain and cause a blockage in a blood vessel (i.e., anembolism). The buildup of the intima may also reinforce the attachmentof the sensor 102 and the anchoring elements 104 to the atrial septum108. As a result, the sensor 102 may be attached to the heart in asufficiently stable manner so as to prevent injury to the heart.

Referring again to FIG. 1, the wireless LAP sensor device 100 may beinserted through the atrial septum 108 in the region of the fossa ovalisin one aspect. The fossa ovalis is typically the thinnest section of theatrial septum and therefore provides a region amenable to septalpuncture as part of the implantation of the wireless LAP sensor device100. In one aspect, the sensor 102 of the wireless LAP sensor device 100may be situated entirely within the left atrium 106 as illustrated inFIG. 1. In other aspects, the sensor 102 may protrude into the atrialseptum 108, the right atria, and other regions of the heart of thepatient.

FIG. 3 is a cross-sectional view of a wireless LAP sensor device 100A inanother aspect. In this other aspect, the device 100A may include acylindrical sensor 102A that includes a proximal sensor end 302projecting into the right atrium 304 and a distal sensor end 306projecting into the left atrium 106 as illustrated in FIG. 3. In thisaspect, the distal sensor end 306 may include a diaphragm 208A exposedto the blood pressure within the left atrium 106. Also in this aspect,the sensor 102A may be held in place by anchoring elements 104A situatedagainst the right wall 110 and the left wall 112 of the atrial septum108. The anchoring elements 104A situated in this manner may providemore robust anchoring forces for the cylindrical sensor 102A in thisaspect; the cylindrical sensor 102A may be larger and/or heavier thanthe rectangular sensor 102 illustrated in FIG. 1.

FIG. 2 is a side cross-sectional view of the rectangular sensor 102 andthe anchoring elements 104 of the wireless LAP sensor device 100illustrated previously in FIG. 1. The sensor 102 may include a housing206 containing a sensor circuit 210 connected to a deformable diaphragm208. The diaphragm 208 is typically exposed to the blood pressure withinthe left atrium (not shown). Left atrial pressure (LAP) within the leftatrium typically exerts a force against the diaphragm 208, causing thedeflection of the diaphragm 208. The sensor circuit 210 is designed todetect changes in the deflection of the diaphragm 208 resulting fromchanges in LAP and to encode those detected changes into a form that maybe read by an external data acquisition device through a process ofinductive telemetry. The LAP measurements from the sensor 102 mayprovide valuable information for diagnosing a variety of cardiacproblems including, but not limited to mitral stenosis and leftventricle failure associated with high LAP. The design and operation ofthe sensor circuit 210 are described in more detail herein below.

Referring again to FIG. 2, one or more anchoring elements 104 may beattached to the housing 206 of the sensor 102. In one aspect, theanchoring elements 104 may include a first anchoring element 202 and asecond anchoring element 204 as illustrated in FIG. 2. The anchoringelements 104 are typically formed from a biodegradable and resilientmaterial capable of being reversibly deformed into a compact foldedconfiguration (not shown) during implantation of the wireless LAP sensordevice 100, typically accomplished using catheter-based surgicalmethods. In addition, the anchoring elements 104 are designed to revertinto an anchoring configuration as illustrated in FIG. 2, typically byelastic rebound of the anchoring elements 104 from their foldedconfiguration.

To facilitate the reversible elastic deformation of the anchoringelements 104 into the folded configuration and back into the anchoringposition, the anchoring elements 104 may be formed from biocompatibleand elastically deformable materials including, but not limited to,memory materials such as NITINOL. In addition, the anchoring elements104 may be shaped and dimensioned to provide relatively flexiblesub-structures including, but not limited to: loops, lobes, and/or armsformed from wires and/or thin sheets of a biocompatible and elasticallydeformable material. A detailed description of the design andconstruction of the anchoring elements 104 in various other aspects isprovided herein below.

a. Anchoring Elements

In various aspects, the wireless LAP sensor device 100 includes at leastone anchoring element 104 to secure the sensor 102 firmly in placewithin the left atrium 106 as described previously. The anchoringelements 104 may be situated against the right wall 110 of the atrialseptum 108, against the left wall 112 of the atrial septum 108, oragainst both the right wall 110 and the left wall 112 of the atrialseptum 108. FIG. 4 is a close-up cross-sectional view of a wireless LAPsensor device 100 situated within the heart of a patient, showing theanchoring forces that secure the sensor 102 firmly in place within theleft atrium 106 in one aspect. The anchoring elements 104 typicallypress against the left wall 112 and/or right wall of the atrial septum108. The forces 402 and 404 generated against the right wall 110 by theanchoring elements 104 situated within the right atrium 304 may beresisted by an opposing force 406 generated against the left wall 112 byeither additional anchoring elements 104 (not shown) situated within theleft atrium 106 and/or a surface 408 of the sensor 102 situated adjacentto the left wall 112. These opposed anchoring forces 402, 404, and 406compress the atrial septum 108 and maintain the sensor 102 in placewithin the left atrium 106. In various aspects, the separation distancebetween the base of the at least one anchoring element 104 and theadditional anchoring elements 104 and/or surface 408 of the sensor 102may be slightly less than the typical thickness of the atrial septum 108and/or the fossa ovalis.

i. Profile and Curvature Along Length of Anchoring Elements

In an aspect, the anchoring elements 104 are designed to be compatiblewith the delivery/retrieval system. In particular, the anchoringelements 104 may be dimensioned to fit within a sheath of anintroductory catheter in a folded configuration. Typically, the foldedanchoring elements 104 may be situated proximally and/or distally to thesensor 102, depending on the particular design of the wireless LAPsensor device 100. As a result, the anchoring elements 104 may eachconsist of an elongated and narrow structure. In an aspect, eachanchoring element 104 may have a general shape or profile including, butnot limited to a flattened lobe, a flattened petal, or a flattened tine.

FIG. 5 is a side view of the wireless LAP sensor device 100 illustratedpreviously in FIG. 2. In this aspect, each anchoring element 202 and 204may have a flattened lobe profile, as illustrated in FIG. 5. In order tofit within the sheath of an introductory catheter in a foldedconfiguration, each anchoring element 202 and 204 may have a maximumwidth 502 that is comparable to the sensor width 504. In another aspect(not shown), the maximum width 502 of each anchoring element 202 and 204may be significantly wider than the sensor width 504. In this otheraspect, the lobe profile of each anchoring element 202 and 204 may becompressed laterally within the sheath of the delivery catheter in thefolded configuration and may then expand to its full width upon releasefrom the sheath and subsequent reversion to the anchoring configuration.As illustrated in FIG. 5, each anchoring element 104 is typicallyrounded at its free end to avoid injury to the atrial septum 108 duringimplantation and subsequent residence in the heart of the patient.

Referring back to FIG. 4, each anchoring element 104 may further includea curvature along its length. In the anchoring configuration, thiscurvature may impart a spring functionality to each anchoring element104, allowing each anchoring element 104 to exert a force against theatrial septum 108. Each anchoring element 104 may be provided with acurvature in any profile capable of imparting the spring functionalityto the anchoring element 104 including, but not limited to a C-shapedprofile, an S-shaped profile, a circular arc profile, and any othersuitable curvature profile.

ii. Wire-Frame Anchoring Elements

Referring back to FIG. 5, each anchoring element 104 may be constructedfrom a thin elongate stock formed from a resilient material includingbut not limited to a wire, resulting in an anchoring element 104 in theform of a wire frame in various aspects. In an aspect, thecross-sectional profile of the wire may be any known shape including,but not limited to a round profile 506, as illustrated in FIG. 5A, or anelliptical, semi-circular, square, rectangular, triangular, or any otherpolygonal cross-sectional profile. In additional aspects, thecross-sectional profile of the wire may be solid or hollow. In otheraspects, the material forming each anchoring element 104 may be cut froma sheet of a suitable material in the desired profile shape; in theseother aspects, the material of each anchoring element 104 may resemble awire with a rectangular or square cross-sectional profile.

iii. Solid Sheet Anchoring Elements

In other aspects, the one or more anchoring elements 104 may be providedin alternative forms to a wire frame form. FIG. 6A is a side view andFIG. 6B is a perspective view of a wireless LAP sensor device 100 inanother aspect. In this aspect, each anchoring element 104 may beprovided in the form of a solid sheet of a resilient material, resultingin paddle-like anchoring elements 602 and 604. These paddle-likeanchoring elements 602 and 604 may have lobe-like profiles andcurvatures similar to the wire frame anchoring elements 202 and 204illustrated in FIG. 5. However, the added material and contact area ofthe paddle-like anchoring elements 602 and 604 relative to the wireframe anchoring elements 202 and 204 may impart additional anchoringforce capability to the paddle-like anchoring elements 602 and 604.

The paddle-like anchoring elements 602 and 604 may possess a curvaturealong the length of these anchoring elements 602 and 604 to impart aspring functionality, but may retain a longitudinal cross-section thatis essentially planar, as illustrated in FIG. 6C. In other aspects, theanchoring elements 104 may have non-linear longitudinal cross-sections.FIG. 7A is a side view and FIG. 7B is a perspective view of a wirelessLAP sensor device 100 in which the longitudinal cross-section of theanchoring elements 104 is formed into a curved profile as illustrated inFIG. 7C, resulting in spoon-like anchoring elements 702 and 704. Thecurved profile may be oriented such that the outer curve 706 is facingaway from the atrial septum as illustrated in FIG. 7; in this aspect,the curved profile may enhance the mechanical strength of the anchoringelements 702 and 704. In another aspect, the curved profile may beoriented such that the outer curve 706 is facing away from the atrialseptum (not shown) which may enhance the contact area between theanchoring elements 104 and the atrial septum. In other additionalaspects, the longitudinal cross-section of the anchoring elements 104may be provided in other forms including, but not limited to: a creasedprofile such as a “V-shaped” profile in which two planar segmentsintersect at an angle along a crease line; a polygonal profile in whichmultiple planar segments intersect at multiple crease lines; a pleatedprofile such as a “W-shaped” profile; a recurved or saddle-shapedprofile, and any other longitudinal cross-section without limitation.

In other aspects, the solid sheet forms of the anchoring elements 104illustrated in FIGS. 6-7 and discussed herein above may further includeone or more discontinuities in the solid sheet form including, but notlimited to: holes, voids, openings, serrations, indentations and orprotrusions along the lateral edges of the anchoring elements 104, andany other discontinuity in the solid sheet material used to form theanchoring elements 104. These discontinuities may be provided to enhancethe function of the anchoring elements 104 in one or more of at leastseveral different manners including, but not limited to: providing localflexibility in a desired region of an anchoring element 104; providing asurface texture that enhances the anchoring force provided by theanchoring element 104; providing a surface texture that inhibits theformation of blood clots and/or enhanced the adhesion of epithelialcells and formation of the intima; providing one or more reservoirs forthe release of active compounds such as anti-inflammatory compounds, andany combination thereof. In yet other aspects, the one ordiscontinuities in the solid sheet form may include additional materialsincluding, but not limited to: local reinforcing members attached to aregion of an anchoring member; protruding surface textural elements suchas protrusions, bumps, ridges, and other textural elements, and anycombination thereof.

iv. Construction of Anchoring Elements

The anchoring elements 104 may be constructed using any biocompatibleresilient material without limitation. Non-limiting examples of suitablebiocompatible resilient materials include metals such as platinum, metalalloys such as stainless steel, memory materials such as NITINOL,silicone, polyurethane, plastic polyether block amide, high densitypolyethylene, silicone rubber, and any other known biocompatibleresilient material. In one aspect, the anchoring elements 104 may beconstructed using a memory material such as NITINOL by etching a desiredanchoring arm 104 shape from a single sheet of material, heat-forming aNITINOL wire or other form into a desired anchoring arm 104 shape, orany combination thereof.

In other aspects, at least a portion of each anchoring element 104, andor a portion of the one or more anchoring elements 104 may beconstructed using a biodegradable material. In these other aspects, thebiodegradable materials may be incorporated to provide for the removalof the wireless LAP sensor device 100 after implantation. In otheradditional aspects, the biodegradable materials may be incorporated as acoating over the anchoring elements 104 to provide additionalfunctionality including, but not limited to: enhanced biocompatibility,timed release of active compounds such as anti-inflammatory compounds,and any combination thereof.

v. Number and Arrangement of Anchoring Elements

In various aspects, the wireless LAP sensor device 100 may include anynumber of anchoring elements 104 without limitation. In various aspectsillustrated in FIGS. 1, 2, and 4-7 and described previously herein, thewireless LAP sensor device 100 may include a pair of anchoring elements104 in various forms. FIG. 8 is a side view of a wireless LAP sensordevice 100 in one aspect that includes a single anchor element 104. Inthis aspect, the single anchor element 104 and the back surface 802 ofthe sensor 102 exert opposing anchoring forces that compress the atrialseptum (not shown) and maintain the sensor 102 in a fixed positionwithin the left atrium (not shown) of the patient.

In other aspects, the wireless LAP sensor device 100 may include betweenone and about twelve anchoring elements 104. In one aspect, theanchoring elements 104 may be situated against the right wall of theatrial septum, against the left wall of the atrial septum, or againstboth the left and right walls of the atrial septum 108. In anotheraspect, the anchoring elements situated against one of the walls of theatrial septum may be uniformly distributed about an axis perpendicularto the surface of the wall. For example, the two anchoring elements 104illustrated in FIG. 1 are separated by an angle of 180 degrees about anaxis perpendicular to the right wall 110 of the atrial septum 108.

FIG. 9A is an end view and FIG. 9B is a side view of a wireless LAPsensor device 100 that includes a “dual propeller” arrangement of sixanchoring elements 104: a set of three proximal anchoring elements 902and a set of three distal anchoring elements 904. Referring to FIG. 9A,the proximal anchoring elements 902 are distributed at even angularintervals about an axis perpendicular to the right wall 110 of theatrial septum 108. In this aspect, the proximal anchoring elements 902are situated against the right wall 110 of the atrial septum 108 and thedistal anchoring elements 904 are situated against the left wall 110 ofthe atrial septum 108. The anchoring forces in this aspect are providedby the anchoring elements 104, rather than by a combination of theanchoring elements 104 and a surface of the sensor 102 as in the variousaspects described previously herein in which all anchoring elements weresituated against the right wall 110 of the atrial septum 108.

When the anchoring elements 104 are in the extended anchoring positionpressing against the atrial septum 108, the proximal anchoring elements902 and the distal anchoring elements 904 may be spaced apart at adistance 906 approximately equal to the thickness of the atrial septum108 in the area of the implanted wireless LAP sensor device 100. Forexample, if the device 100 is implanted in the region of the fossaovalis the separation distance 906 may be about 3-4 mm. In an aspect, abiasing mechanism may be provided to provide a force to pull theproximal anchoring elements 902 and the distal anchoring elements 904together to enhance the anchoring forces provided by the anchoringelements 104. The biasing mechanism may be adapted to press the proximalanchoring elements 902 and/or distal anchoring elements 904 against thewalls of the atrial septum 108.

In one aspect, the biasing mechanism may be a spring mechanism thatprovides pressure on the walls of the atrial septum 108 and pulls theproximal anchoring elements 902 and/or distal anchoring elements 904flat against the atrial septum 108 to maintain a low profile for theanchoring elements 104 and the sensor 102. The spring mechanism mayinclude a metal spring, a spring made from other materials with strongmaterial memory, and any other suitable spring. In an aspect, the springmay be constructed from a material including, but not limited to MP35N,nickel chrome alloys or other suitable biocompatible materials.

The implantation of the wireless LAP sensor device 100 in this aspect isaccomplished using additional modifications of the catheter-basedimplantation methods to provide for the situation of the atrial septumbetween the proximal anchoring elements 902 and the distal anchoringelements 904. The method of implanting the wireless LAP sensor device100 that includes the dual propeller arrangement of anchoring elements104 is described in further detail herein below.

FIG. 10 is a side view of a wireless LAP sensor device 100 in anadditional aspect that includes four anchoring elements 104 situatedagainst the left wall 112 of the atrial septum 108. In this additionalaspect, the anchoring is further provided by an enlarged proximalsegment 1002 of the sensor 102 defining a flattened proximal face 1004.The proximal face 1004 is situated against the right wall 110 of theatrial septum 108 and generates an anchoring force opposite to theanchoring forces generated by the four anchoring elements 104. In oneaspect, the proximal face 1004 may have a width of 0.25 mm to 4 mm toprovide a surface onto which the atrial septum 108 may be pressed toclamp the atrial septum 108 in place in relation to the sensor 102. Inaddition to providing a robust clamping surface for anchoring the device100, the enlarged proximal segment 1002 may also impede any potentialembolization of the device 100 within the left atrium of the patient.

FIG. 11 is a side view of a wireless LAP sensor device 100 in anotheradditional aspect. In this aspect, the anchoring elements 202 and 204are provided in the form of a wire frame similar to the device 100illustrated in FIG. 5. In this aspect, an additional biocompatiblematerial is attached to the anchoring elements 202 and 204 to formelastic webs 1102 and 1104, respectively. The elastic webs 1102 and 1104may provide one or more of at least several enhancements to the functionof the anchoring elements 202 and 204. The elastic webs 1102 and 1104may enhance the structural integrity or elastic properties of theanchoring elements 202 and 204. The elastic webs 1102 and 1104 mayincrease the contact area between the anchoring elements 202 and 204 andthe adjacent wall of the atrial septum 108, resulting in enhancedanchoring forces; the material forming the elastic webs 1102 and 1104may be impregnated with active compounds such as anti-inflammatorycompounds to accelerate the healing of the atrial septum and/or toencourage the overgrowth of epithelial cells and the formation of theintima in the heart of the patient. Non-limiting examples of suitablematerials for the construction of the elastic webs 1102 and 1104include: silicone rubber, polyurethane and/or any other suitableflexible biocompatible material.

vi. Additional Features of Anchoring Elements

In various embodiments, the anchoring elements 104 may incorporateadditional features to enhance the function of the anchoring elements104. FIG. 12 is a perspective view of a wireless LAP sensor device 100in which a silicone disc 1202 is attached near the base 1204 of theanchoring elements 104 in an aspect. When the device 100 is implanted,the silicone disc 1202 is situated adjacent to the right wall of theatrial septum (not shown) along with the anchoring elements 104. Therelatively large size of the silicone disc 1202 prevents the anchoringelements 104 from working through the atrial septum and instigating anembolism of the device 100 in the left atrium of the patient. Any shapeof silicone disc 1202 may be used in various aspects without limitation.However, the thin disk shape provides a low profile, which may inhibitthe formation and release of blood clots and may further encourage theovergrowth of epithelial cells within the right atrium to form theintima. In addition, the round shape of the silicone disc 1202 providesa reliable minimum dimension (analogous to a round manhole cover) whichmust pass through the atrial septum 108 to provoke an embolism of thedevice 100.

In an aspect, the anchoring elements 104 may include one or moreradioopaque marker materials adhered to or embedded into the anchoringelements 104. Non-limiting examples of radioopaque marker materialsinclude heavy metals such as tantalum and platinum. The marker materialsmay be used in conjunction with a medical visualization technology suchas fluoroscopy to monitor the position of the anchoring elements 104 todetermine one or more positions of the one or more anchoring elements104 to provide positional feedback during the implantation procedure andthe confirm proper deployment of the anchoring elements 104.

The marker materials may be attached at any position on the anchoringelements 104 without limitation. In one aspect, the marker materials maybe attached near the free end of one or more anchoring elements 104; thedistance between the one or more free ends of the anchoring elements 104as determined from the relative positions of the free ends may be usedas an additional indication of the configuration of the anchoring arms104, and/or to confirm the deployment of the anchoring elements 104 froma folded position to an anchoring position during implantation of thedevice 100. In another aspect, one or more marker materials may beattached to or embedded within two or more anchor elements 104 such thatthe two or more anchor elements 104 may be individually identifiedand/or differentiated from one another using a medical visualizationtechnology such as fluoroscopy. In this aspect, each of the two or moreanchor elements 104 may be marked using a unique marker material, usinga unique pattern or position, or any combination thereof.

In one illustrative example, one or more marker materials may beincorporated into a device 100 that includes a “dual propeller”arrangement of the anchoring elements 104 similar to the deviceillustrated in FIG. 9. In this example, the marker materials may beattached to or embedded to the anchoring elements 104 in such a way thatthe proximal anchoring elements 902 may be differentiated from thedistal anchoring elements 904 using a medical visualization technologysuch as fluoroscopy. During the implantation of the device, thisdifferentiation between the proximal anchoring elements 902 and thedistal anchoring elements 904 may facilitate the proper placement ofthese two groups of anchoring elements 104 on opposite sides of theatrial septum.

In another additional aspect, the anchoring elements 104 may be coatedwith at least one surface-modifying material to impart a desiredphysical, chemical, or biological characteristic to the surface of theanchoring elements. In one aspect, the anchoring elements 104 may becoated with a hydrophilic coating. In this aspect, the hydrophiliccoating may reduce the friction on the anchoring elements 104 to enablesmooth delivery through the sheath or other catheter-based surgicalinstruments during implantation of the device 100. Suitable hydrophiliccoating materials may also be selected to be biocompatible and non-toxicover the course of long-term and chronic residence of the device 100 inthe heart of the patient. Non-limiting examples of suitable hydrophiliccoating materials include: silica; silicones; other hydrophilic polymerssuch as polyvinyl pyrrolidone, polyethylene glycol, polyethylene oxide,polyethyloxazoline, polypropylene oxide, polyacrylamide, polyvinylalcohol, carboxylmethyl cellulose, hydroxymethyl cellulose, hyaluronicacid and any other known biocompatible and hydrophilic coatingmaterials.

In an additional aspect, the anchoring elements 104 may also include amedicating sleeve or may be composed of materials impregnated withactive compounds. This medicating sleeve or impregnated material maycontain active compounds to be introduced into the heart, applied to theseptal wall or placed in the bloodstream during the implantation of thewireless LAP sensor device 100. In one aspect, the medicating sleeve orimpregnated material may be silicone rubber, polyurethane or any othersuitable biocompatible material impregnated with the active compound.The active compound may be provided in the form of a powder to be mixedwith the biocompatible material to form a ring, sleeve or similarstructure to be situated on one or more anchoring elements 104. Theactive compound in the medicated sleeve or impregnated material may betime released, contact released or released through any other suitablemechanism known in the art. In one aspect, the medicated sleeves orimpregnated material may be impregnated with anti-inflammatory agentssuch as various types of steroid. In this aspect, the introduction ofthe anti-inflammatory agent may hasten the healing around the holeformed in the atrial septum during implantation and/or may facilitatethe build up of intima.

b. Sensor

Referring back to FIG. 2, the wireless LAP sensor device 100 includes asensor 102 in various aspects. The sensor 102 includes a housing 206containing a sensor circuit 210 that is connected to a deformablediaphragm 208. The sensor circuit 210 is configured to measure leftatrial pressure (LAP) within the heart of a patient using capacitivepressure measurement methods and to wirelessly communicate the measuredpressures to an external data acquisition device using inductivetelemetry methods.

FIG. 13 is an exploded side view of the sensor 102 in one aspect with aportion of the housing 206 removed to view the housing's interior. In anaspect, the housing 206 defines a cavity 1302 within which the sensorcircuit 210 is hermetically sealed beneath the diaphragm 208 to protectthe sensor circuit 210 from moisture or ingress of body fluids. Thesensor circuit 210 includes an inductive coil 1304, a fixed capacitorplate 1306, and a moveable capacitor plate 1308. The fixed capacitorplate 1306 is electrically connected to the inductive coil 1304 at afirst end 1310 via a first lead 1312. The moveable capacitor plate 1308is electrically connected to the inductive coil 1304 at a second end1314 via a second lead 1316. In addition, the moveable capacitor plate1308 is attached to an inner surface 1318 of the diaphragm 208. Thesensor circuit 210 is situated within the cavity 1302 and the diaphragm1318 is sealed over an opening 1320 formed in the upper face 1322 of thehousing 206.

The fixed capacitor plate 1306 and the moveable capacitor plate 1308together form a variable capacitor that is electrically connected inseries with the inductive coil 1304 to form an LC circuit. This LCcircuit intrinsically possesses a characteristic resonant frequency thatmay vary depending on the particular capacitance of the variablecapacitor. The capacitance may vary depending on the position of themoveable capacitor plate 1308, which shifts position along with thediaphragm 208 depending on the pressure applied to the external surface1324 of the diaphragm 208. Thus, the resonance frequency of the LCcircuit formed by the components of the sensor circuit 210 may encodethe left atrial pressure (LAP) when the sensor 102 is situated withinthe left atrium of a patient. A more detailed description of theelectrical function of the sensor circuit 210, including the measurementand encoding of LAP and the wireless transmission of the measured LAP toan external data acquisition device are provided herein below.

i. Housing

The housing 206 provides a hermetically-sealed protective covering forthe internal sensor circuit 210, a support surface for the moveablediaphragm 208, and in certain aspects, an anchoring surface to hold thesensor 102 fixed in place, for example as illustrated in FIG. 1. Inaddition, the housing 206 is designed to provide these functions withminimal interference with the operation of the diaphragm 208 andassociated sensor circuit 210. Further, the housing 206 may be designedto facilitate the implantation of the wireless LAP sensor device 100, tominimize the formation and release of blood clots within the left atriumof the patient, and to enhance the adhesion of epithelial cells andassociated formation of the intima within the left atrium.

In various aspects, the housing 206 may be formed from a biocompatible,non-conductive, and non-metallic material. Non-limiting examples ofsuitable materials for the construction of the housing 206 include:fused silica, quartz, ceramic, and sapphire. In one aspect, the housingmaterial may be selected to enable wireless induction/telemetry tofunction without any interference or shielding that a metallic housingwould create; in this aspect, fused silica and quartz may be selected.In another aspect, the material may be selected for ease of fabrication.In this other aspect, the selected material may be compatible with theselected method of fabrication including, but not limited to: machining,casting, and microfabrication methods such as deposition, and anycombination thereof.

The external shape of the housing 206 may be any shape capable ofenclosing an internal cavity 1302 without limitation. In one aspect, thehousing 206 may have a rectangular or prismatic shape, as illustrated inFIG. 1, for example. In this aspect, a rectangular or prismatic shapemay potentially be easier to manufacture and may also leverage existingsensor designs and manufacturing processes known in the art. In anotheraspect, the housing 206 may have a cylindrical shape, as illustrated inFIG. 3, for example. In this other aspect, the cylindrical housing shapemay facilitate the delivery and implantation of the wireless LAP sensordevice 100 using modifications of existing catheter-based deliverymethods. For example, the housing 206 may have a circular, ovoid orother rounded shape to fit through a primary lumen of a deliverycatheter and to fit through a passage formed in a septal wall of theheart by a needle. In addition, the cylindrical housing shape may resultin a low profile of the sensor 102 within the left atrium 106 of thepatient during use. This low profile design may reduce the risk ofdeveloping or releasing blood clots and may be more amenable to theformation of the intima during an extended and chronic residence of thedevice 100 within the heart of the patient.

ii. Diaphragm

Referring back to FIG. 13, the sensor 102 includes a flexible diaphragm208 coupled to the sensor circuit 210. The diaphragm 208 may be sealedover an opening 1320 formed in the upper face 1322 of the housing 206 toform the hermetically-sealed cavity 1302 containing the sensor circuit210. FIG. 14 is an exploded diagram illustrating one technique forattaching the flexible diaphragm 208 to the housing 206 in one aspect.In this aspect, the diaphragm 208 may be provided in the form of a thindisk that is sealed around the circumference of a support surface 1402provided on the upper face 1322 of the housing 206. FIG. 15 is anexploded diagram illustrating another technique for attaching theflexible diaphragm 208 to the housing 206 in another aspect. In thisother aspect, the diaphragm 208 may be formed with a lip 1502 that isplaced over the seat 1504 provided on the upper face 1322 of the housing206. Thus, an inside surface of the lip 1502 may, for example, beadhered to an outside surface of the seat 1504. The diaphragm 208 may beattached to the housing 206 using a variety of techniques including, butnot limited to laser welding and adhesive attachment (e.g., using anepoxy).

In use, the diaphragm 208 deflects in response to the net forceresulting from differences in the pressure inside and outside thehousing 206. The pressure outside the housing 206 may be the left atrialpressure (LAP) when the sensor 102 is situated within the left atrium ofthe patient. Depending on the condition of the patient, LAP may rangefrom about 0.01 mm Hg to about 100 mm Hg. Without being limited to anyparticular theory, the mean LAP in a healthy patient may be about 12 mmHg, and the peak LAP in patients with various heart conditions may rangefrom about 10 mm Hg to about 60 mm Hg or higher, depending on theparticular type of heart condition and the severity of the heartcondition.

In various aspects, the pressure inside the housing 206 may range fromabout 0.01 mm Hg to about 100 mm Hg. Pressure, as used herein, refers tothe gage pressure in a system, defined as the pressure above or belowatmospheric pressure; the atmosphere has a gage pressure of about 0 mmHg by this definition. Without being limited to any particular theory,the sensitivity of the diaphragm 208 to relatively small changes in LAPmay be enhanced by matching the pressures inside and outside of thehousing 206. If pressure inside the housing 206 is equal to the mean LAPand the sensor 102 is situated in the left atrium of the patient, no netforce would be exerted in the diaphragm 208 when the LAP was equal tothe mean LAP. In this situation, small changes in LAP above or below themean LAP would exert relatively small net forces on the diaphragm 208.As a result, a relatively thin diaphragm 208 may be used due to therelatively low range of anticipated forces acting on the diaphragm 208.In addition, the diaphragm 208 may undergo a smaller range ofdeflections in this situation, allowing the diaphragm 208 to operatewell within the linear elastic region of the material from which thediaphragm is constructed. The pressure inside the housing 206 may beachieved by sealing the diaphragm 208 to the housing 206 under pressureconditions matched to the desired pressure inside the housing.

In another aspect, the gage pressure inside the housing may be equal toabout 0 mm Hg if the diaphragm 208 is sealed to the housing 206 underatmospheric conditions. In this aspect, the diaphragm 208 may deflectinwards when situated within the left atrium and when exposed to LAPlevels in excess of 0 mm Hg. As a result, the range of forcesanticipated to act on the diaphragm 208, and the anticipated range ofdeflections of the diaphragm 208 may be higher than if the pressureinside the housing 206 was more closely matched to the mean LAP.

In various aspects, the diaphragm 208 may be a precision micromachinedstructure that may undergo a deflection during use ranging from about 1nanometer to about 100 micrometers in order to provide a frequencyresponse suitable for the measurement of the hemodynamic parametersassociated with regular as well as irregular heartbeats. The diaphragm208 may be constructed using any suitable biocompatible and elasticmaterial. Non-limiting examples of materials suitable for theconstruction of the diaphragm include: silica, silicon, quartz,titanium, stainless steel, MP35N and any other known suitable material.In one aspect, the diaphragm 208 may be micromachined from fused silicaor fused quartz.

Referring back to FIG. 13, the movable capacitor plate 1308 may beattached to the inner surface 1318 of the diaphragm 208. In one aspect,an insulating layer of epoxy of other coating may be laid down on theinner surface 1318 of the diaphragm 208 and the moveable capacitor plate1308 may be attached using the epoxy adhesive. In this aspect,deflections of the diaphragm 208 alter the separation distance betweenthe moveable capacitor plate 1308 and the fixed capacitor plate 1306,inducing a corresponding shift in the resonance frequency of the sensorcircuit 210. In this aspect, the diaphragm 208 may be constructed from anon-conductive material such as fused silica or fused quartz to minimizethe electrical interference of the diaphragm 208 with the function ofthe sensor circuit 210.

In another aspect, the diaphragm 208 may be formed from an electricallyconductive material. Non-limiting examples of suitable electricallyconductive materials include: metals such as titanium; and doped siliconmaterials, such as highly doped SiB or SiGeB. In this other aspect, theconductive diaphragm 208 may function as the moveable capacitor plate1308, obviating the need to attach a dedicated moveable capacitor plate1308 to the diaphragm 208. Due to the elimination of the dedicatedmoveable capacitor plate 1308 and associated adhesive, the diaphragm 208may be more sensitive to changes in pressure in this aspect compared toa diaphragm 208 with an attached moveable capacitor plate 1308 asdescribed previously herein.

iii. Sensor Circuit

Referring back to FIG. 13, the sensor 102 includes a sensor circuit 210electrically attached to the diaphragm 208 and sealed within the cavity1302 formed within the housing 206 in various aspects. FIG. 16A is acutaway side view and FIG. 16B is a cutaway top view of a sensor 102illustrating the relationship of the various components of the sensorcircuit 102 in one aspect. The sensor circuit 210 includes an inductivecoil 1304 electrically connected in series to a variable capacitor madeup of a fixed capacitor plate 1306 and a moveable capacitor plate 1308.The fixed capacitor plate 1306 is electrically connected to theinductive coil 1304 at a first end 1310 via a first lead 1312. In thisaspect, the first lead 1312 may provide at least some structural supportto hold the fixed capacitor plate 1306 in a stationary position withinthe housing 206. The diaphragm 208 in this aspect is constructed of athin disk of a conductive material such as titanium and functions as themoveable capacitor plate 1308 as described previously herein. Thediaphragm 208 is electrically connected to a second end 1314 of theinductive coil 1304 via a second lead 1316. An outer edge 1602 of thediaphragm 208 may be sealed to a circumferential step 1604 formed in thein the upper face 1322 of the housing 206. The diaphragm 208 sealed tothe upper face 1322 of the housing 206 define the cavity 1302 containingthe sensor circuit 210

The sensor circuit 210 measures left atrial pressure using capacitivepressure measurement methods. The inductive coil 1304, fixed capacitorplate 1306, and moveable capacitor plate 1308 are electrically connectedin series to form a resonant circuit. FIG. 17 is a schematic diagramillustrating an idealized resonant sensor circuit 1700. The resonantsensor circuit 1700 includes the inductor coil 1702 with an inductanceL_(s) in series with a variable capacitor 1704 with a capacitance C_(s).Without being limited to any particular theory, the resonant frequency fof this resonant sensor circuit 1700 may be expressed in terms of L_(s)and C_(s) according to Eqn. I:

$\begin{matrix}{f = \frac{1}{2\pi \sqrt{L_{s}C_{s}}}} & {{Eqn}.\mspace{14mu} (I)}\end{matrix}$

The capacitance C_(s) of the resonant sensor circuit 1700 is influencedby the separation distance of the moveable capacitor plate 1308 from thefixed capacitor plate 1306 of the sensor 102. This separation distancemay change as a result of the deflection of the diaphragm 208 inresponse to changes in the left atrial pressure (LAP).

The resonant frequency f of the resonant sensor circuit 1700 may beobtained using inductive telemetry methods. Referring again to FIG. 17,a data acquisition device 1708 that includes an external antenna coil1706 may be used to perform the inductive telemetry in one aspect. Thedata acquisition device 1708 may communicate with the resonant sensorcircuit 1700 via a magnetic coupling 1710 of the external antenna coil1706 with the induction coil 1702 of the resonant sensor circuit 1700.This magnetic coupling 1710 inductively transfers power from the dataacquisition device 1708 to the resonant sensor circuit 1700. Thistransferred power energizes the resonant sensor circuit 1700, whichreflects back a load impedance to the acquisition device 1708 inresponse. Using electrical engineering methods well-known in the art,the resonant frequency f of the resonant sensor circuit 1700, and byextension the LAP, may be determined. In one aspect, the magnitude ofthe reflected impedance from the sensor circuit 1700 may be used todetermine the resonant frequency f. In another aspect, the phase of thereflected impedance may be used to determine the resonant frequency f.In an additional aspect, spectral analysis of the reflected impedancemay be performed to determine the resonant frequency f of the resonantsensor circuit 1700.

The range of resonant frequencies f may be influenced by the particularvalues of the sensor's inductance L_(s) and capacitance C_(s). Theparticular values of L_(s) and C_(s) incorporated into the resonantsensor circuit 1700 may be determined using standard electricalengineering principals. For example, L_(s) may be influenced by thenumber of coils and coil dimensions in the inductive coil 1304. Inanother example, the capacitance C_(s) may be influenced by the size,shape, separation distance, and materials used in the construction ofthe fixed and moveable capacitor plates, as well as the stiffness andsurface area of the diaphragm.

iv. Additional Sensor Features

In an aspect, the sensor 102 may include one or more radioopaque markermaterials adhered to or embedded into the sensor 102. Non-limitingexamples of suitable radioopaque marker materials include heavy metalssuch as tantalum and platinum. The marker materials may be used inconjunction with a medical visualization technology such as fluoroscopyto monitor the position of the sensor 102 and/or to provide positionalfeedback during the implantation procedure. The marker materials may beattached at any position on the sensor 102 without limitation.

In one aspect, the sensor 102 may also include a sleeve constructed of abiocompatible material including, but not limited to silicone. FIG. 18Ais a perspective view and FIG. 18B is a side view of a sleeve 1802mounted on a proximal end 1804 of the sensor 102. The sleeve 1802 may beshaped to fit snugly over the proximal end 1804 of the sensor 102 andmay further cover the one or more anchoring elements 104 at eachelement's point of attachment to the sensor 102.

In this aspect, the sleeve 1802 may facilitate the insertion of thesensor 102 into the left atrium of the patient. The material of thesleeve 1802 may smooth potentially discontinuous transitions such as thejoining of the attached ends of the anchoring elements 104 to theproximal end 1804 of the sensor 102. In addition, the sleeve 1802 may becoated and/or impregnated with any one or more materials to facilitatethe insertion of the sensor 102 and to enhance the biocompatibility ofthe sensor during chronic residence in the left atrium of the patient.Non-limiting examples of materials suitable for incorporation into thematerial of the sleeve 1802 include: one or more radioopaque markermaterials described herein previously to provide positional feedbackduring implantation and/or retrieval; hydrophilic coatings to reduce thefriction of the sensor 102 during deposition and/or retrieval; activecompounds to reduce inflammation, inhibit the formation and release ofblood clots, and to facilitate the adhesion of epithelial cells andassociated formation of the intima within the left atrium of thepatient, and any combination thereof.

The sleeve 1802 may further include a knob 1806 projecting away from theproximal end 1804 along an axis of symmetry 1808 of the one or moreanchoring elements 104 to facilitate the snagging and/or retrieval ofthe sensor 102 from the patient. The knob 1806 may include a reduceddiameter neck 1810 or circumferentially extending groove that mayprovide a region to which a tether may be attached during implantationand/or retrieval of the sensor 102.

FIG. 19A is a perspective view and FIG. 19A is a side view of a sleeve1802 in another aspect that further includes an extension plug 1902extending along the axis of symmetry 1808 of the one or more anchoringelements 104 to further facilitate the snagging and/or retrieval of thesensor 102 from the patient. In this other aspect, the extension plug1902 may be attached to the knob 1806 by a flexible lanyard 1904 tofacilitate the snagging of the extension plug 1902 by a tether duringthe implantation and/or retrieval of the sensor 102.

In the various aspects described herein above, the sleeve 1802 may becoated and/or impregnated with am active compound. This medicatingsleeve or impregnated material may contain active compounds to beintroduced into the heart, applied to the septal wall or placed in thebloodstream during the implantation of the wireless LAP sensor device100. In one aspect, the medicating sleeve or impregnated material may besilicone rubber, polyurethane or any other suitable biocompatiblematerial impregnated with the active compound. The active compound maybe provided in the form of a powder to be mixed with the biocompatiblematerial to form the sleeve 1802. The active compound in the medicatedsleeve or impregnated material may be time released, contact released orreleased through any other suitable mechanism known in the art. In oneaspect, the medicated sleeves or impregnated material may be impregnatedwith anti-inflammatory agents such as various types of steroid. In thisaspect, the introduction of the anti-inflammatory agent may hasten thehealing around the hole formed in the atrial septum during implantationand/or may facilitate the build up of intima.

In other aspects, the sensor 102 may further include one or morebioactive coatings to enhance the biocompatibility and function of thesensor 102 during extended chronic implantation in the left atrium ofthe patient. The sensor may include a coating that includes a bioactivecompound to discourage excessive tissue overgrowth or thrombusformation. The diaphragm 208 may include a coating to encourage theadhesion of epithelial cells and the formation of the intima.

In another additional aspect, the sensor 102 and/or sleeve 1802 may becoated with at least one surface-modifying material to impart a desiredphysical or chemical characteristic to the surface of the sensor 102. Inone aspect, the sensor 102 may be coated with a hydrophilic coating. Inthis aspect, the hydrophilic coating may reduce the friction on thesensor 102 to enable smooth delivery through the sheath or othercatheter-based surgical instruments during implantation and/or retrievalof the device 100. Suitable hydrophilic coating materials may also beselected to be biocompatible and non-toxic over the course of long-termand chronic residence of the device 100 in the heart of the patient.Non-limiting examples of suitable hydrophilic coating materials include:silica; silicones; other hydrophilic polymers such as polyvinylpyrrolidone, polyethylene glycol, polyethylene oxide,polyethyloxazoline, polypropylene oxide, polyacrylamide, polyvinylalcohol, carboxylmethyl cellulose, hydroxymethyl cellulose, hyaluronicacid, and any other known biocompatible and hydrophilic coatingmaterials

II. Methods of Using Wireless LAP Sensor

In various aspects, the wireless LAP sensor device 100 may be implantedand/or retrieved using modifications of catheter-based surgical methodsas performed by the elements of a delivery/retrieval system. Thedelivery/retrieval system and implantation/retrieval methods in thesevarious aspects ensure the fail-safe delivery of the device 100 andprovide for repositioning and/or extraction of chronic implants.

FIG. 20 is a flow chart illustrating a method 2000 of implanting thewireless LAP sensor device 100 in an aspect. The method 2000 includes aset of initial steps common to the implantation of all devices 100, andat least two sets of specialized final steps to complete theimplantation of the device 100, taking into account the configurationand locations of the anchoring elements 104 relative to the atrialseptum of the patient.

Side views of several components of a delivery/retrieval system areillustrated in FIGS. 21A-C. FIG. 21A is a diagram of one aspect of anintroducer catheter 2100 or sheath. In this one aspect, the introducercatheter 2100 may have a proximal end with a housing 2102. The catheter2100 may be formed of polyether block amide, high density polyethylene,silicone rubber, polyurethane or other materials. The materials used toform the catheter 2100 may be biocompatible to prevent complicationduring insertion procedures.

In one aspect, the housing 2102 may be formed to couple to other devicesor components. For example, the housing 2102 may be formed to receive adilator, needle or similar component. The proximal end of the catheter2100 may also include openings to a set of lumens 2106 within thecatheter 2100. As used herein “set” refers to any number of itemsincluding one. The catheter 2100 may contain any number of lumens. Thelumens may run the length of the catheter or only run over a portion ofthe catheter 2100. The lumens may include a primary lumen 2106. Thecatheter 2100 may have a diameter large enough to allow insertion ofother components such as a dilator, needles and leads. The diameter maybe small enough to enter and traverse the vascular system of a patient.In one embodiment, the diameter of the catheter 2100 may be 1-10 mm. Theprimary lumen 2106 may have a diameter sufficient to receive a lead,dilator, needle or other components.

In one aspect, the catheter 2100 may be a deflectable catheter. Thecatheter 2100 may be manipulated to curve at its distal end 2108 tofacilitate insertion. In a further embodiment, the catheter may beprecurved. The catheter 2100 may include a main body 2110. The main body2110 may have any length. In one embodiment, the main body 2110 hassufficient length to traverse an intravenous path to the right atrium ofa heart. The housing 2102 may include a mechanism 2112 to control thedistal end 2108 of the catheter 2110 as it is advanced into a patient.The mechanism 2112 may be a lever as illustrated in FIG. 21A, a controlstick, a handle or other mechanism to control the curve of the distalend 2108 of the catheter 2100 using a wire line system or similarsystem. The distal end 2108 may contain or be covered with a marker 2114to assist in the insertion process. The marker 2114 may be a heavy metalsuch as tantalum or similar substance that is visible via fluoroscopy orother system for tracking instruments in a patient, similar to theradioopaque markers described previously herein above.

FIG. 21B is a diagram of one aspect of a dilator 2116. The dilator 2116may have a housing 2118 at the proximal end, a long tubular body 2120and a distal tip 2122. The long tubular body 2120 may define an innerlumen 2124. The inner lumen 2124 and body 2120 may be flexible to assistduring insertion of the dilator 2116. The dilator 2116 may be formedfrom silicon rubber, polyurethane, polyether block amide, high densitypolyethylene and other materials. The diameter of the dilator 2116 maybe between 1-8 mm. In one embodiment, a portion of the dilator 2116 nearthe distal tip 2112 may have a larger outer diameter. In one embodiment,the length of this enlarged portion may be 5-8 mm. The length of atypical distal end may be 1-5 mm.

FIG. 21C is a diagram of one aspect of a needle 2126. The needle 2126may have a proximal end 2128 with an enlarged diameter. The proximal end2128 may be formed to be coupled to other instruments and devices. Forexample, the proximal end 2128 may be coupled to a dye injection deviceor similar device. The proximal end 2128 may also include an opening toan interior lumen 2130 or set of lumens. These lumens may run the entirelength of the needle 2126 or over a portion of the needle 2126. Theneedle 2126 may be formed from a flexible material to allow it to followthe path of a dilator 2116 or catheter 2100 through a vascular system ofa patient to the heart. In one embodiment, the needle 2126 may bepartially or fully formed from steel, Nitinol (an alloy of nickel andtitanium), or another alloy or metal. The needle 2120 may have adiameter of 0.25 to 3 mm or any other suitable diameter.

In one aspect, the distal end of the needle 2120 may form a point 2132.The point 2132 may be sufficiently sharp to puncture through organicstructures. The end point 2132 may also be open allowing access to theinterior lumen 2130. In another embodiment, the needle 2126 may be solidwith a solid tip 2132.

Referring back to FIG. 20, the method 2000 of implanting the wirelessLAP sensor device 100 includes inserting a catheter and needle at step2002 to advance the needle into the right atrium of the patient andreleasing a dye into the right atrium at step 2004 to confirm properplacement of the catheter. The dye may be used in connection withfluoroscopy or similar techniques and systems for monitoring instrumentposition in the body of a patient. The distal end of the catheter may bepositioned adjacent to the atrial septum and the fossa ovalis. Theneedle then penetrates the atrial septum at step 2006 and dye isreleased into the left atrium at step 2008 to confirm proper placementof the catheter. The release of dye or other markers may continuethrough the process of penetration or may be restarted just afterpenetration of the septal wall. The dilator is then advanced through thehole formed in the atrial septum at step 2010 to enlarge the hole formedby the needle, followed by advancement of the catheter and sheaththrough the enlarged hole at step 2012.

Once the catheter and sheath have been advanced through the atrialseptum at step 2012, the remaining steps of the method 2000 performed tosituate and anchor the wireless LAP sensor device 100 may differdepending on the particular design of the device. In one aspect, theremaining steps may depend on whether the device 100 includes anchoringelements situated adjacent to the right wall of the atrial septum, asillustrated for example in FIG. 1, or whether the device 100 includesanchoring elements situated adjacent to both the left and right walls ofthe atrial septum, as illustrated for example in FIG. 3.

FIGS. 22A-C are cutaway side views of a sheath 2202 containing awireless LAP sensor device 100 of the embodiment of FIG. 2. Initiallythe device 100 is in a folded configuration (FIG. 22A) that isprogressively advanced at step 2012 of the delivery method 2000 untilthe device 100 exits the sheath 2202 (FIG. 22B) and the anchors 104 areallowed to fully expand (FIG. 22C) once the device 102 extends throughthe heart wall (FIG. 22D). In this aspect, the wireless LAP sensordevice 100 is similar to the device 100 illustrated in FIG. 2. As shownin FIG. 22A, the sensor 102 is situated near the distal end 2204 of thesheath 2202 and the anchoring elements 104 in the folded configurationextend in a proximal direction 2206 toward a guide tube 2208. The freeends of the anchoring elements 104 may be attached to one or moretethers 2210 protruding from the distal end 2212 of the guide tube 2208.The sheath 2204 maintains the device 100 in a folded configurationduring the situation of the sensor 102 within the left atrium of thepatient. In addition, as shown in FIG. 22B, the sheath may be made toslide in a proximal and/or distal direction to expose at least a portionof the device 100 during implantation. As the sheath 2202 is slid in aproximal direction 2206 to expose portions of the device, those parts ofthe device that are constructed of elastic elements, such as theanchoring elements 104, may elastically rebound to revert to theunfolded configuration suitable for anchoring the device 100, asillustrated in FIG. 22C to be implanted or anchored in the heart wall asshown in FIG. 22D.

In one aspect, the one or more tethers 2210 may control the position ofthe sensor 102 and anchoring elements 104 during implantation. Inaddition, the one or more tethers may be reattached to the anchoringelements, sensor housing, or any other suitable snagging structureincorporated into the device 100 in order to retrieve the device 100 ifnecessary.

The remaining steps of the method 2000 may differ depending on thedesign of the device 100 to be implanted.

a. Implanting Rectangular/Prismatic Sensor

To accomplish the anchoring of a device 100 that includes a sensor 102with a rectangular or prismatic profile, similar to the devicesillustrated in FIGS. 1-2, the remaining steps of the method 2000 entailpositioning the sensor 102 adjacent to the left wall of the atrialseptum and the anchoring elements 104 adjacent to the right wall of theatrial septum.

Referring back to FIG. 20, the catheter and sheath were advanced intothe left atrium at step 2012. As can be understood from FIGS. 22B-D, atstep 2014, the catheter and sheath are withdrawn together to situate thesensor against the left wall of the atrial septum within the left atriumand the anchoring bodies within the right atrium; the atrial septum issituated between the sensor and the anchoring elements. At step 2016,the sheath is withdrawn to deploy the anchor elements in the rightatrium (FIG. 22D). The tether can be used to adjust the positioning ofthe device in the heart wall and, once a desired positioning andanchoring arrangement is achieved, the tether can be detached, per step2018. The catheter and sheath can then be withdrawn from the patient(step 2020).

A similar method of implantation may be used for devices 100 thatinclude snaring elements such as the knob 1806 and/or extension plug1902 as illustrated in FIGS. 18A-19B with minor modifications. For aspecific discussion regarding the delivery of the device embodiment ofFIGS. 19A-B, reference is made to FIGS. 23A-F, which are cutaway sideviews of a sheath 2202 containing a wireless LAP sensor device 100 beingprogressively deployed. A tether snare loop 2210 is attached to theextension plug 1902 of the device at step 2022. The device is initiallyin a folded configuration (FIG. 23A) that is progressively advanced atstep 2024 of the delivery method 2000 until the device 100 exits thesheath 2202 (FIG. 23B) and is extended through the heart wall (FIG.23C). As can be understood from FIG. 23C, although the device extendsthrough the heart wall, the anchoring elements 104 remain encased insideof the sheath 2202 at the completion of step 2024, thereby maintainingthe anchoring elements 104 in a folded position.

Once the device extends through the heart wall, the anchors 104 are thenallowed to fully expand (FIG. 23D-E). Specifically, the sheath iswithdrawn to deploy the anchoring elements at step 2026. After thecompletion of step 2026, the anchors 104 and device 102 act on the heartwall (FIGS. 23F-G) to anchor the device in place. The sensor 102 is nowsituated in the left atrium 106 and the anchoring elements 104 aresituated in the right atrium 304. The tether 2210 remains attached tothe extension plug 1902 after the completion of step 2026 to provide ameans of adjusting the position of the device 100 and/or removing thedevice 100 if needed.

After confirming proper placement of the sensor and anchoring elements,and/or performing any final adjustments to the positions of the sensorand/or anchoring elements, the tether is detached from the extensionplug 1902 at step 2030. Specifically, the tether may then be detached byoperating a mechanism at the proximal end of the snare catheter at step2030. If the sensor was deployed incorrectly, the tether can be used topull the sensor back into the sheath and then redeployed in the correctposition. The catheters and sheath may then be withdrawn fromcirculation at step 2032 to complete the implantation of the device.

The method of implantation discussed above with respect to theembodiment of FIGS. 19A-B and FIGS. 23A-G may be used for the device 100that includes a snaring element in the form of a knob 1806 with minormodifications.

b. Implanting Cylindrical Sensor

To implant a device 100 that includes both proximal and distal anchoringelements 104, such as the cylindrical sensor illustrated in FIG. 3, amodified method 2000 may be used. The device 100, which is attached tothe tether within the sheath, may be advanced through sheath until thedistal anchoring elements are deployed at step 2034. The sensor andsheath are then withdrawn together until the distal anchor elements areflush with septum wall in the left atrium at step 2036. The sheath onlyis then withdrawn until the proximal anchoring elements are deployedagainst the septum wall in right atrium at step 2038. As illustrated inFIG. 24, the tether may then be detached at step 2040 and the cathetersand sheath may then be withdrawn from circulation at step 2042 tocomplete the implantation of the device.

c. Method of Extracting Sensor

In various aspects, the device 100 may be extracted from the patientusing a procedure that is essentially the reverse of the deploymentmethod 2000 illustrated in FIG. 20. A catheter-based snare may be usedto grab the extension plug 1902, knob 1808, or other snagging structureincorporated into the device 100. Once the device 100 is snagged, thedevice 100 may be withdrawn from the atrial septum by applying tractionto the extension plug 1902, knob 1808 or other snagging structure viathe snare. An outer sheath provided with the catheter may be used toprovide counter-traction and to facilitate the deformation of theanchoring elements 104 into the folded configuration within the sheath,allowing for the safe extraction of the device 100.

The foregoing merely illustrates the principles of the technologydisclosed herein. Various modifications and alterations to the describedembodiments will be apparent to those skilled in the art in view of theteachings herein. It will thus be appreciated that those skilled in theart will be able to devise numerous systems, arrangements and methodswhich, although not explicitly shown or described herein, embody theprinciples of the disclosed technology and are thus within the spiritand scope of the disclosed technology. From the above description anddrawings, it will be understood by those of ordinary skill in the artthat the particular embodiments shown and described are for purposes ofillustrations only and are not intended to limit the scope of thedisclosed technology. References to details of particular embodimentsare not intended to limit the scope of the disclosed technology.

What is claimed is:
 1. A wireless and leadless left atrial pressuremeasurement device configured for delivery through a thickness of anatrial septum via a minimally invasive delivery tool, the devicecomprising: a wireless pressure sensor comprising a proximal portion, adistal portion opposite the proximal portion, and a housing containing ahermetically sealed cavity containing a sensor circuit; a firstanchoring element comprising a first distal end and a first freeproximal end generally opposite the first distal end, the first distalend operably coupled to the wireless pressure sensor, the firstanchoring element extending proximally away from the proximal portion;and a second anchoring element comprising a second distal end and asecond free proximal end generally opposite the second distal end, thesecond distal end operably coupled to the wireless pressure sensor, thesecond anchoring element extending proximally away from the proximalportion; wherein, when the first and second anchoring elements are freeto assume a biased state, the first free proximal end and second freeproximal end extend in generally opposite directions and the firstanchoring element projects generally distally.
 2. The wireless andleadless left atrial pressure measurement device of claim 1, wherein thefirst anchoring element is configured such that, when the device isbeing delivered via the delivery tool, the first anchoring element isdeflected away from the biased state via the delivery tool such that thefirst and second free proximal ends are in close proximity to each otherand projecting generally proximally away from the proximal portion. 3.The wireless and leadless left atrial pressure measurement device ofclaim 1, wherein, in the biased state, the first free proximal end is inclose proximity to the distal region as compared to the second freeproximal end.
 4. The wireless and leadless left atrial pressuremeasurement device of claim 1, wherein, in the biased state, the firstanchoring element extends along a longitudinal side of the wirelesspressure sensor offset from the longitudinal side.
 5. The wireless andleadless left atrial pressure measurement device of claim 1, wherein, inthe biased state, the first anchoring element extends along alongitudinal side of the wireless pressure sensor offset from thelongitudinal side.
 6. The wireless and leadless left atrial pressuremeasurement device of claim 1, wherein, in the biased state, the firstanchoring element and the wireless pressure sensor combine to form aclamping arrangement.
 7. The wireless and leadless left atrial pressuremeasurement device of claim 6, wherein the clamping arrangementcomprises a distance between the first anchoring element and thewireless pressure sensor that is slightly less than the thickness of theatrial septum.
 8. The wireless and leadless left atrial pressuremeasurement device of claim 1, further comprising a silicone disc sealimmediately adjacent the proximal portion and through which at least oneof the first or second anchoring element extends.
 9. The wireless andleadless left atrial pressure measurement device of claim 1, furthercomprising a feature extending from the proximal region and configuredfor engagement by a tether of the delivery tool.
 10. The wireless andleadless left atrial pressure measurement device of claim 9, wherein thefeature comprises a knob extending from the proximal region.
 11. Thewireless and leadless left atrial pressure measurement device of claim10, wherein the feature comprises a knob, an extension plug and alanyard, wherein the lanyard is attached to the knob at one end and asecond end of the lanyard is attached to the proximal region.
 12. Thewireless and leadless left atrial pressure measurement device of claim1, wherein the first anchoring element comprises a biocompatibleresilient material.
 13. The wireless and leadless left atrial pressuremeasurement device of claim 12, wherein the biocompatible resilientmaterial is selected from: platinum, NITINOL, silicone, polyurethane,plastic polyether block amide, high density polyethylene, siliconerubber, and any combination thereof.
 14. The wireless and leadless leftatrial pressure measurement device of claim 1, wherein at least one ofthe first anchoring element or the second anchoring element furthercomprises an elongated and narrow structure selected from: a wire frameanchoring element comprising a thin elongate stock formed into a loop,wherein both ends of the elongate stock are operably coupled to thewireless pressure sensor; and a solid sheet anchoring element comprisinga flat sheet.
 15. A wireless and leadless left atrial pressuremeasurement device configured for delivery through a thickness of anatrial septum via a minimally invasive delivery tool, the devicecomprising: a wireless pressure sensor comprising a proximal portion, adistal portion opposite the proximal portion, and a housing containing ahermetically sealed cavity containing a sensor circuit; a firstanchoring element supported on the wireless pressure sensor between theproximal and distal portions and comprising first and second wingsspaced apart from each other and, when the first and second wings are ina biased state, the first and second wings extend radially outward fromthe wireless pressure sensor; and a second anchoring element supportedon the wireless pressure sensor between the proximal and distal portionsand comprising third and fourth wings spaced apart from each other and,when the third and fourth wings are in a biased state, the third andfourth wings extend radially outward from the wireless pressure sensorand the third and fourth wings face the first and second wings in anopposed, spaced apart fashion.
 16. The wireless and leadless left atrialpressure measurement device of claim 15, wherein the first and secondanchoring elements are configured such that, when the device is beingdelivered via the delivery tool, the first, second, third and fourthwings are deflected away from the biased state via the delivery toolsuch that the first and second wings project generally distally and thethird and fourth wings project generally proximally.
 17. The wirelessand leadless left atrial pressure measurement device of claim 15,wherein, in the biased state, the first anchoring element and the secondanchoring element combine to form a clamping arrangement.
 18. Thewireless and leadless left atrial pressure measurement device of claim17, wherein the clamping arrangement comprises a distance between thefirst and second wings and the third and fourth wings that is slightlyless than the thickness of the atrial septum.
 19. The wireless andleadless left atrial pressure measurement device of claim 1, furthercomprising a feature on or near the proximal region and configured forengagement by a tether of the delivery tool.
 20. The wireless andleadless left atrial pressure measurement device of claim 15, whereinthe first anchoring element comprises a biocompatible resilientmaterial.
 21. The wireless and leadless left atrial pressure measurementdevice of claim 20, wherein the biocompatible resilient material isselected from: platinum, NITINOL, silicone, polyurethane, plasticpolyether block amide, high density polyethylene, silicone rubber, andany combination thereof.
 22. A wireless and leadless left atrialpressure sensor, the sensor comprising: a housing containing ahermetically sealed cavity, wherein the sealed cavity opens at anopening defined within a surface of the housing; a flexible diaphragmsealed over the opening to complete the hermetically sealed cavity; anda sensor circuit comprising: an induction coil comprising a first endand a second end; a fixed capacitor plate electrically connected to thefirst end of the induction coil; and a moveable capacitor plateelectrically connected to the second end of the induction coil andmechanically attached to the flexible diaphragm; wherein the sensorcircuit is contained within the hermetically sealed cavity.
 23. Thedevice of claim 22, wherein: the fixed capacitor plate and the moveablecapacitor plate form a variable capacitor; a capacitance of the variablecapacitor varies as a function of a deflection of the flexible diaphragmin response to a left atrial pressure on the diaphragm; the inductioncoil and the variable capacitor form a resonant circuit comprising aresonant frequency; and the resonant frequency varies in response to achange in the left atrial pressure.
 24. The device of claim 23, whereinthe left atrial pressure may be obtained using a data acquisition devicecomprising an external antenna coil, wherein: the external antenna coilmagnetically couples with the induction coil of the sensor to transferpower to the sensor; the resonant frequency of the sensor is determinedby an analysis of a load impedance of the sensor during the powertransfer; and the left atrial pressure is determined using apredetermined calibration of pressure as a function of resonancefrequency.
 25. The device of claim 23, wherein the housing isconstructed from a non-conductive material selected from: fused silica,quartz, ceramic, and sapphire.
 26. The device of claim 23, wherein thediaphragm is constructed from a non-conductive material selected from:fused silica, quartz, ceramic, and sapphire.
 27. The device of claim 23,wherein the diaphragm is constructed from a conductive material selectedfrom: highly doped silicon and titanium, wherein the diaphragm and themoveable capacitor plate are integrated into a single structure and thediaphragm is electrically connected to the second end of the inductioncoil.
 28. The device of claim 23, wherein the diaphragm deflects to amaximum deflection ranging from about 1 nanometer to about 100micrometers.
 29. The device of claim 23, wherein the housing furthercomprises an external shape selected from: a rectangular shape, aprismatic shape, and a cylindrical shape.